At most there could be 40 contest winners. If 30 go to publishers he’s left with 120. if each winner can get 3 pieces of work, divide how much artwork he has(120) by the minimum amount of artwork he sends to a winner(3), and you get 40. there could be less depending on if he sends 5 pieces, for example, as a bonus for random winners. The max amount of winners he can have is 40.